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Патент USA US3031521

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,
United States Patent
3,03 1,5 l l
ice
Patented Apr. 24, 1 962
1
2
TABLE I
3,031,511
GLYCOL DIETHER INHIBITORS
Robert J. Zellner, Marinette, Wis., and Charles A. R.
Johnson, Menominee, Mich., assignors to Ansul Chem
ical Company, Marinette, Wis., a corporation of Wis
Ethers:
Ethylene glycol dimethyl ether __________ __ 85
Diethylene glycol dimethyl ether __________ __ 162
Triethylene glycol dimethyl ether ________ .. 216
Tetraethylene glycol dimethyl ether _______ __ 275
consin
No Drawing. Filed Oct. 30, 1959, Ser. No. 849,710
8 Claims. (Cl. 260-6115)
This invention relates to the protection of glycol di
Ethers and Their Inhibitors
Boiling point, ‘’ C.
Inhibitor:
10
ethers against decomposition using heterocyclic nitrogen
compounds as stabilizers.
Glycols and their ethers tend to decompose on heating
or on prolonged storage or exposure to air, forming acids
N~methy1 pyrrolidine ________________ __ 78-80
N-butylene pyrrole ____________________ __
155
N-hexyl pyrrolidine __________________ __
201
3,5-dibutyl pyridine ___ _______________ __
271
Homologs of'the inhibitors enumerated in Table I also
and other active hydrogen compounds including water. 15 are effective inhibitors and may be used to inhibit homo—
logs of the ethers.
The inhibitors are readily soluble in the ethers and there
indicating that the reaction mechanism may be one of ~ is no special problem involved in adding the inhibitors
These decomposition products tend to build up or ac
cumulate even when the ethers are stored under nitrogen,
auto-oxidation. This is a serious ‘problem since these
beyond agitating to insure dispersion.
glycol ethers are used as reaction media for such'reagents 20 When glycol diethers such as diethylene glycol dimethyl .
as Grignards, metallic sodium and metal hydrides, which
ether are stored for a prolonged period of time, even under
react with these decomposition products and active hydro
nitrogen and in the dark, they gradually build up active
gen compounds.
'
_ g
hydrogen impurities and water. The active hydrogen
It is an object of this invention to provide‘a practical
impurities
be determined by the Zerewitinoil proced
and highly e?ective method for substantially reducing the 25 ure and thecan
water can be determined by the Karl Fisher
formation of these decomposition products. It is a further
method. We have also determined that the amount of
object of this invention to provide an inhibitor which
will protect the ether in the vapor phase as well as the
decomposition which takes place in diethylene glycol di
methyl ether under normal storage at room temperature
liquid phase. It is a still further object of this invention
over a period of 24 months can be approximated by re
to provide an inhibitor which is not easily separated from 30
?uxing theether in the presence of air for 100 hours. A
the ether by distillation when such separation is not de
comparison of our. heterocyclic compounds with com
sired. It is a still further object of this invention to pro
pounds suggested by the prior art is shown in Table II,
vide inhibitors which are relatively inert to metallic
the last three compounds.
sodium. It is an additional object of this invention to
A sample of diethylene glycol dimethyl ether was in
provide inhibitors which can be distilled at ordinary pres 35
hibited
with 0.5% N-butylene pyrrole and 0.5% 3,5-di
sures without decomposition. Glycol diethers of the for
butyl pyridine which produced results comparable to
mula RO(CH2CH2O),,R’, where R and R' are alkyl
those obtained with 1.0% of either compound used alone.
groups having 1 to 4 carbon atoms and n is a number
Some of the tests were repeated with the inhibitor at a
from one to four, are used as inert reaction media for
concentration
of 0.1%. The ether containing inhibitor
such reactions as the Grignard reaction and sodium con 40
at this level showed less buildup of active hydrogen im
densations and in other places where it is desirable to
purities than the uninhibited control sample as shown
have a dry medium of good solvent power. For these
in the following Table II, but the results were less re
uses the phenolic type inhibitors, such as disclosed in
produceable. More than 1% inhibitor may be used, but
US. Patent 2,114,832 cannot be used since they react
with the reagents to give undesirable products. The amine 45 since it is the desirable solvent properties of the ethers
which determine their use in a reaction, and not those
type compounds which are disclosed as inhibitors in U.S.
of the inhibitor, there seems to be little advantage in add
Patents 2,132,017 and 2,044,800 have boiling points which
ing more inhibitor than is necessary.
are frequently widely divergent from the boiling point of
the ether which they are intended to protect. Thus, these
inhibitors do not inhibit the ether in the vapor phase, 50
and when the ether is recovered by distillation the inhibitor
is removed.
TABLE II
[Dlethylene glycol dimethyl ether at 160° C.—100 hours]
Since the glycol ethers have boiling points which vary
with their molecular weight, it is necessary to supply in
hibitors having a range of boiling points. For example, 55
dimethoxy diethylene glycol boils about 162° C. and
can be suitably inhibited with N-butylene pyrrole which
boils at 155° C. Dimethoxy tetraethylene glycol boils
at 275° C. and can be suitably inhibited with 3,5-dibutyl
pyridine which boils at 271° C. The very narrow spread 60
between the boiling point of the ether'and its inhibitor
insures that except by the most e?icient fractionation they
will not become separated during recovery operations.
Inhibitor
Concen
Inhibitor
tration,
Weight
Impurities at
Impurities at
Start
Finish
Active
Active
H2O, Hydrogen H2O, Hydrogen
percent percent calculated percent calculated
percent
None .---------------. . --
as
.‘
3,5-D1bntyl pyridine“
Q33
percent
as:
.
.45
Q77
Pyridine ____________ ._
0. 12
0. 36
N-hexylpyrrolidine...
N ~butylene pyrrole.--_
It is also obvious, however, that if it is desired to remove
the inhibitor, it can be accomplished by reversing the 65 N-methyl pyrrolldlne_
N-methyl pyrrole_____
inhibitor ether combination, that is, for example, inhibit
Dibutyl amineing dimethoxy diethylene glycol with 3,5-dibutyl pyridine.
Dihexyl amine...
Hydroxy anisole__
A few ethers and an appropriate inhibitor for each are
0.
8: 21
0.
0‘ 34
64
0_. 52
92
0.65
0. 57
0. 55
listed in Table I below.
0.. 34
0.30
0. 19
0.19
3,031,511
3
4
rolidine, 3,5-dibutyl pyridine, N-methyl pyrrole and mix
A second test procedure was developed in which the
glycol ethers were heated in cylinders of either glass or
tures of the foregoing.
2. A glycol diether having the formula
steel at a temperature of 230-260 C. Prior to ?lling, the
cylinders were evacuated to less than 0.01 mm. of mer
cury and the increase in pressure within the cylinder on
heating was measured as an indication of the extent of
where R and R" are alkyl groups having 1 to 4 carbon
decomposition which occurred. The results obtained
with several inhibitors are indicated in the following
inhibitor at least about 0.1% by weight of a N-butylene
Table III.
atoms and n is a number from 1 to 4, containing as an
pyrrole.
From these data it will be readily observed ‘
3. Ethylene glycol dimethyl ether inhibited with at least
that 3,5-dibutyl pyridine is not only a good inhibitor, but 10
about 0.1% by weight N-rnethyl pyrrolidine.
is superior to many compounds usually employed for
4. Diethylene glycol dimethyl ether inhibited by at
this purpose.
least about 0.1% by weight N-butylene pyrrole.
TABLE III
[Tetraethylene glycol dimethyl ether at 450° F.—24 hours]
15
Inhibitor
Pressure Rise
None
15. 6
20. 4
Diphenyl amine, 1% __________ ..
32. 4
24. 9
N-amino propyl morpholine, 1%
15. 4
15. 4
Dodecyl amine, 1% __________ __
3,5-Dibutyl pyridine, 1% ____________________________ _.
22. 6
8.3
1S. 2
8. 9
7. The method of inhibiting decomposition of a glycol
diether having the formula RO(CH2CH2O),,R’, Where R
and R’ are alkyl groups having one to four carbon atoms
and n is a number from 1 to 4, which comprises dissolv
ing in said ether from about one to ten‘ parts by weight
of a heterocyclic nitrogen compound selected from the
From the foregoing description, it will be apparent that
a variety of different compositions may be utilized in prac
ticing the present invention. It is to be understood that
group consisting of N-methyl pyrrolidine, N-butylene
pyrrole, N-hexyl pyrrolidine, 3,5-dibutyl pyridine, N~
the foregoing speci?c compositions should be considered
methyl pyrrole and mixtures of the foregoing to approxi
mately 1000 parts by weight of said ether.
merely as illustrative embodiments of the present inven~
tion and that modi?cations and changes may be made
which are intended to be included within the scope of
the appended claims.
5. Triethylene glycol dimethyl ether inhibited by at
least about 0.1% by weight N-hexyl pyrrolidine.
6. Tetraethylene glycol dirnethyl ether inhibited by
at least about 0.1% by Weight 3,5-dibutyl pyridine.
8. The method of inhibiting decomposition of a glycol
diether having the formula RO(CH2CH2O),.,R', where R
30 and R’ are alkyl groups having 1 to 4 carbon atoms and
We claim:
n is a number from 1 to 4, which comprises dissolving
1. A glycol diether having the formula
in said ether at least about 0.1% by weight N-butylene
R0 (CH2CH2O ) nR’
Where R and R’ are alkyl groups having 1 to 4 carbon 35
atoms and n is a number from 1 to 4, contain'ing‘as an
inhibitor at least about 0.1% by weight of a heterocyclie
nitrogen compound selected from the group consisting of
N-methyl pyrrolidine, N-butylene pyrrole, N-hexyl pyr
pyrrole.
References Cited in the ?le of this patent
UNITED. STATES PATENTS
2,476,554
Lincoln et a1. ________ _.. July 19, 1949 .
2,736,709
2,936,290
Glickman et al _________ __ Feb. 28, 1956
Gysling et al. ________ __ May 10, 1960
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